<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

        <style>
            .box1{
                width: 200px;
                height: 200px;
                background: red;
                padding: 30px;
                border: 10px solid chartreuse;

                /* 标准盒模型 */
                box-sizing: content-box;
            }

            .box2{
                width: 200px;
                height: 200px;
                background: green;
                margin-top: 100px;

                padding: 30px;
                border: 10px solid chartreuse;

                /* 怪异盒模型 */
                box-sizing: border-box;

                
            }
        </style>

</head>
<body>
    
    <div class="box1"></div>
    <div class="box2"></div>
</body>
</html>